This invention relates generally to apparatus used to produce a water sanitizing product containing a halogen compound. More specifically, the improved apparatus relates to the design of a spray dryer and its use in combination with a fluid bed dryer and agglomerating apparatus to produce fast dissolving granular product, such as bleaching and sanitizing agents for body of water like calcium hypochlorite.
Bleaching and sanitizing agents for use in bodies of water, particularly in the sanitation and disinfection of swimming pool waters, have been commercially utilized for a number of years. Calcium hypochlorite has been a particularly effective agent because of its relative stability and its being an inexpensive solid oxidizing agent that uses its available chlorine to remove impurities and kill pathogenic organisms in water.
Calcium hypochlorite has been manufactured or proposed for manufacture from lime and sodium hydroxide by a number of processes that attempt to produce the highest quality product that is contaminate free in the most cost effective manner. Exemplary of these different processes are the use of a slurry containing crystals of calcium hypochlorite dihydrate in a concentrated aqueous solution of calcium hypochlorite and sodium chloride, or other inorganic halides, or the admixing of a wet cake of calcium hypochlorite in a cutting type mixer with dry fines in sufficient proportion to decrease water content to the desired level. U.S. patent application Ser. No. 898,841, filed Aug. 19, 1986 by Bridges, now abandoned and assigned to the assignee of the present invention, discloses a process to produce calcium hypochlorite particles with the use of a turbine agglomerator. Still another approach was developed using spray graining techniques to produce the desired product granules by the spraying and drying of calcium hypochlorite slurries.
Most recently, a process producing a hypochlorinated acid by the mixing and reaction of an alkali metal hydroxide and a chlorine gas has been perfected to provide the chlorinating agent that can be used to produce calcium hypochlorite.
There has been a continuing need to develop a fast dissolving granular product that is dust free and, especially in the area of swimming pool chemical product manufacture, that permits longer operating times of the equipment without the need for maintenance because of the corrosive nature of the product and the reactants employed. Similarly, the nature of the product produced in swimming pool chemical product manufacture requires ease of handling.
Previous processes, and the apparatus employed in these processes, have suffered from not achieving substantially complete reactions between the halogen and the alkali metal hydroxide, or have produced product that has not been sufficiently dry to facilitate handling. The sizing of the particles has been a continuing problem since oversized particles contain excessive moisture so that caking results and the caked mass adheres to apparatus surfaces, increasing the maintenance time required and causing damage to equipment. Alternately where a drier product was obtained, the final product produced by previous processes had excessive dust which resulted in loss of desired product and disintegration of products into difficult to handle and aesthetically unattractive product masses for consumers.
These problems are solved by the present invention wherein improved apparatus and a process are employed to produce a fast dissolving granular product for thermally sensitive materials.